Nerve excitability

How readily nerve cells respond to stimulation. A rapid rise in pH and the associated fall in ionized calcium can increase excitability, contributing to tingling, muscle stiffness, or tetany. Nerves in the hands, feet and around the mouth often react first, which is why tingling tends to start there. The effect is temporary and reverses when breathing slows. Tingling that appears without over-breathing, or does not fade, should be checked by a doctor.